The US Spent Nuclear Fuel Management System: Emerging Issues

Complex Systems Group, LLC
The US Spent Nuclear Fuel Management System:
Emerging Issues
Dr. Thomas A. Cotton
Complex Systems Group LLC
Briefing to the Nuclear Regulatory Commission
September 18, 2014
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Planned Elements of Spent Nuclear
Fuel (SNF) Management System
• At-reactor storage
Only active element today
• Consolidated storage
• Geologic repository
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•
•
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1980 – fears of running out
of reactor storage space
1980s – demonstration of
dry storage casks for low
burnup fuel
Expectation with federal
waste acceptance in 2000
– ~4000 MTU (peak) in dry
storage at reactors
– ~36,000 MTU (peak) in
pool storage at reactors
Today – most reactor sites
have dry cask storage
– ~20,000 MTU in dry
storage increasing at
~ 2000 MTU/ year
– ~50,000 MTU in pools
At-Reactor Storage:
What Has Changed?
140,000
120,000
2010: 65,000 MTU discharged
2025: 96,000 MTU discharged
2050: 133,000 MTU discharged
Dry storage at >70 sites by 2030
100,000
80,000
60,000
Pool Storage Inventory
40,000
20,000
Dry Storage Inventory
2010
2020
2030
Estimated dry storage
systems:
2010 – 1,400 loaded
2025: ~3,700 loaded
2060: ~9,500 loaded
2075: ~10,800 loaded
2040
2050
2060
Source: Electric Power Research Institute
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Decommissioned Plant Storage as
Emerging Element of the System
1980s expectation – shutdown
sites would be cleared of spent fuel
quickly with federal acceptance
beginning ~2000
Wave of shutdowns starting in
2030s and acceptance delayed to
2025 or later make that
questionable
Ability to move storage canisters
soon after shutdown may be
limited even after acceptance
begins if current trends continue
– Increasing burnups (up to 65 GWd)
– Higher-capacity canisters (up to 37
PWR assemblies)
– Higher thermal limits for storage (up
to 40kW) than for transportation
(up to ~25 kW)
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160,000
CUMULATIVE MTU AT ALL REACTOR SITES
CUMULATIVE MTU AT SHUTDOWN SITES
140,000
120,000
100,000
80,000
60,000
40,000
20,000
2010
2020
2030
2040
2050
2060
2070
2080
2090
Spent fuel at reactor sites assuming no
movement to central location
Source: Hamal, et al., Spent Nuclear Fuel Management: How
centralized interim storage can expand options and reduce costs
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Clearing Spent Fuel from Shutdown
Sites Could Be an Extended Process
• Largest dry storage canisters
loaded to storage thermal
limits with high-burnup fuel
may have to cool on site for
decades before they can be
moved (red curve)
• Removal of bare fuel from
reactor sites in transportation
casks loaded to transportation
thermal limits could allow for
earlier clearance of shutdown
sites (blue curve)
80
70
60
50
40
30
20
10
YEAR
2080
2100
Chart Source: Derived from presentation by Jeffrey Williams, U.S.
Department of Energy , at the Nuclear Waste Technical Review
Board workshop on spent fuel, November 18-19, 2013
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Implications
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• Fuel storage at shutdown reactor sites will become an
increasingly important part of the spent fuel management system
• Designs and regulatory approaches are needed to reduce delay
between storage canister loading and transportation offsite
• Uncertainties about transportability of canisters after extended
storage suggest timely movement to central facilities to avoid
repackaging at shutdown reactor sites
• Centralized facilities may need to accept uncanistered fuel to
minimize post-shutdown storage at reactor sites
• Update of storage and transportation regulations should address
these issues
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Centralized Storage
• Perennial recommendation of policy reviews
• Monitored Retrievable Storage (MRS) included in
Nuclear Waste Policy Act (NWPA)
• MRS included in DOE plans until mid-1990s
– As integral part of system, not just a way to accept
SNF until a repository is available
• BRC recommended prompt action on storage
• Administration’s Strategy for the Management and
Disposal of Used Nuclear Fuel and High-Level
Radioactive Waste calls for consolidated storage
facility(ies)
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Changed Expectations about
Central Storage
• Central facility designs have assumed dry storage in
single standard canister systems
– MRS: receive bare fuel, store in MRS-specific DPC
– Private Fuel Storage : receive and store single DPC system
– Yucca Mountain: receive both Transportation-AgingDisposal canisters (TADs) and DPCs (immediately
repackaged into TADs), for aging or direct disposal
• Central storage facility now may receive and store
multiple types and ages of already-loaded canisters
• Storage period may be much longer than expected
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Implications
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• Central storage facility design and licensing issues
will be more complex than previously anticipated
• Potential new licensing issues should be identified
and addressed as soon as possible
– Pilot facility for 12 shutdown plant sites will need to handle:
• 17 different canister designs,
• 8 different storage overpack designs
• 8 different transport overpack designs
– Larger scale storage facility may require large-scale receipt
and handling of bare fuel assemblies
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Repository
• Geologic repository is still the desired end-state of
the system
– NWPA focused on repository development
– BRC urged prompt action towards a repository
– Administration’s Strategy includes progress on a
repository with site selection by 2026
• Generic repository regulations need to be updated
early in the siting process (BRC)
• Preclosure and postclosure issues need to be
addressed
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Preclosure Issues
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• Repository surface facilities may conduct same
activities as a central storage facility
• Part 63 is risk-informed, Parts 71 and 72 are not,
leading to potentially different regulatory
treatment of same activities at different locations
• Updated regulations should aim for uniform
treatment of spent fuel management activities
wherever they are performed
– Avoid regulatory differences that could drive system
decisions (e.g. location of repackaging)
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Post closure Issues
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• Dramatic escalation of expectations about required scope of site
characterization had major impact on NWPA repository program
– 1981 NRC estimate: underground test facility with two shafts and up
to 1,000 feet of tunnels, costing $25 million to $30 million* ; Yucca
Mountain Exploratory Studies Facility had >5 miles of tunnels
– Escalation of cost estimates to ~$1B per site by 1987 was an important
contributor to decision to limit characterization to a single site
• Federal budget constraints might not accommodate both
central storage and a similar repository siting process
• Updated generic repository regulations should establish
reasonable expectations for a decision-focused site
characterization process, based on experience to date
– WIPP and Yucca Mountain
– Other countries (Sweden, Finland, Canada) that engage the licensing
process with more streamlined site characterization
*U.S. Nuclear Regulatory Commission, ‘ ‘Disposal of High- Level Radioactive Wastes in Geologic Repositories: Licensing
Procedures,” Federal Register, vol. 46, No. 37, Feb. 25, 1981, p. 13973,
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System Issues
• Growing interest in staged, adaptive development with
significant evolution of activities and facilities over time
• Existing regulations were not developed with that in
mind, although the NAS One Step at a Time study
recognized “there are no restrictions precluding DOE
from implementing Adaptive Staging”
• BRC recommendation – “Standards for a disposal facility
should explicitly recognize and facilitate an adaptive,
staged approach to development”
• Also applicable to central storage facility that may evolve
from a pilot focused on accepting only canistered fuel to
a large-scale facility accepting bare fuel
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Complex Systems Group, LLC
Conclusions
• Regulations now in place may be challenged by:
– More complex central storage facility design and
licensing issues than previously anticipated
• Receipt and storage of multiple canister designs after
various periods of storage at reactor sites
• Large scale receipt and handling of bare fuel assemblies
– Need for more streamlined and timely repository
site characterization
• Issues should be identified and addressed as
soon as possible
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Complex Systems Group, LLC
Thank you for your attention
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